The present invention relates to a variable reluctance motor comprising at least one core movable relative to at least one stator and more specifically to a variable reluctance motor core and stator having improved tooth geometry.
Variable reluctance motors are used as direct drive motors for machines that perform repeated applications requiring a high degree of accuracy. These motors include phase assemblies comprised of one or more motor cores, and elongated stators that control the movement of tools such as robotic arms and placement heads along first and second axes. During the operation of certain machines, the motor cores and their respective stators move linearly relative to each other via magnetomotive force. The relative movement between motor core and stator causes the robotic arm or placement head to move from a first position to a second position. However, this position to position movement must be completed with a high degree of precision and at a high velocity under varying load conditions.
In some conventional linear actuated motors, the cores and stators are formed by securing a stack of members, such as laminations, together along adjoining faces. Each core member includes a plurality of adjacent teeth that extend along a longitudinal axis of the core, or lamination. The teeth of each core are intended to guide magnetic flux to the tooth surface. In some motors, stator members are also provided with teeth.
Conventional tooth shapes utilized in motors comprise adjacent teeth configured such that adjoining teeth sides form a U or V shape, or combinations of U and V shapes. For example U.S. Pat. No. 4,647,802 to Konecny discloses a tooth having a generally inverted V shape. However, the tip of the tooth includes a small untapered section having uniform width. This tooth shape comprises a straight tip portion extending from the tooth surface towards a base portion. In some variations of the conventional design, the base portion is rectangular. However, in conventional tooth geometry, regardless of the shape of the base portion, the tip portion of the tooth is a straight section. It has been found that the shape of these conventional tooth sides, while effective in directing flux, is not optimal for directing flux to the tooth surface.
The invention provides a motor core movable relative to a stator. The motor core and the stator core comprise base members and a plurality of adjacent tooth members with improved geometry. Each tooth member comprises a tooth surface and tooth sides. The tooth sides extend from the tooth surface toward the base member. At least one of the tooth sides comprises a tip portion and a base portion. The tip portion extends from the tooth surface to the base portion. The base portion extends from the tip portion to an adjoining base portion of a tooth side of an adjacent tooth member. The tip portion is curved.